1. Field of the Invention
The present invention relates to an organic light emitting diode display device and a method for driving the same.
2. Discussion of the Related Art
Flat panel display (FPD) devices are advantageous for miniaturization and weight reduction thereof, and thus have been widely used for monitors of desktop computers as well as portable computers such as laptop computer and PDA, mobile cellular phones, and the like. These FPD devices include liquid crystal display (LCD) devices, plasma display panel (PDP) devices, field emission display (FED) devices, and organic light emitting diode (OLED) display devices.
Of these, the OLED display devices have advantages of a fast response speed, a luminance with high luminous efficiency, and a large viewing angle. Generally, as for the OLED display device, a data voltage is applied to a gate electrode of a driving transistor by using a switch transistor turned on by a scan signal, and an organic light emitting diode emits a light by using the data voltage supplied to the driving transistor. That is, the current supplied to the organic light emitting diode is controlled by the data voltage applied to the gate electrode of the driving transistor. However, respective driving transistors formed in pixels have a deviation of the threshold voltage (Vth) due to characteristics of the manufacturing process. The current supplied to the organic light emitting diode may have a level different from a designed level due to the deviation of the threshold voltage among the driving transistors, and thus the level of the luminance may be different from a desired level.
To solve this problem, a method of compensating picture quality has been employed in which the non-uniformity of luminance is reduced by sensing characteristic parameters (threshold voltage and mobility) of driving transistors for respective pixels and then appropriately correcting input data depending on the sensing results.
For example, according to the external compensation method disclosed in Korean Patent Publication No. 10-2013-0036659 (titled “Method of Measuring Characteristics of Transistor in Organic Light Emitting Diode Display Device”), a current source is positioned out of pixels, a predetermined current is applied to organic light emitting diodes through the current source, the resultant voltages are measured, and the deviation of the degradation among the organic light emitting diodes is compensated.
As for the widely known techniques for compensating picture quality, a slow mode sensing method and a past mode sensing mode are respectively employed in order to detect threshold voltage characteristics and mobility characteristics of driving transistors. In addition, the respective sensing methods adopt different manners and require an additional memory for storing offset values.
Therefore, new approaches for more efficiently detecting threshold voltage characteristics and mobility characteristics of driving transistors have been sought.